人骨形成蛋白2基因克隆及真核表达载体的构建

在大肠杆菌中克隆人骨形成蛋白2基因并获得真核表达载体。由人成骨瘤细胞中提取总RNA，利用逆转录PCR方法扩增获得人骨形成蛋白2基因cDNA；将此基因片段重组到pGEM-T克隆载体中，转化到大肠杆菌DH5α后，蓝白斑筛选阳性克隆，利用限制性酶切、PCR扩增和核苷酸序列分析鉴定重组质粒；将pGEM-T克隆载体中人骨形成蛋白2基因重组到pcDNA3．1真核表达载体中，用限制性酶切和PCR扩增鉴定重组质粒。结果表明：重组在两种质粒中的基因片段为人骨形成蛋白2基因全编码序列。克隆获得人骨形成蛋白2基因．并得到此基因的真核表达载体，为人骨形成蛋白2的表达打下了基础。     

西尼罗I型病毒亚克隆的构建及其鉴定

目的构建西尼罗病毒基因组的cDNA亚克隆，为西尼罗病毒全长cDNA克隆的研发和应用打下基础。方法根据基因组中限制性酶切位点的分布设计4对引物，QIAamp RNA抽提试剂盒提取西尼罗病毒培养细胞BHK-21的总RNA，长片段RT-PCR技术扩增目的基因片段。将目的基因片段与pMD18-T载体进行连接，转化人感受态细胞E.coli DH5α，进行蓝白斑筛选后得到阳性克隆。将重组质粒进行PCR和测序鉴定。结果获得的目的基因片段经PCR和测序结果表明西尼罗病毒功能基因正确地克隆进入载体。结论成功获得西尼罗I型病毒功能基因的cDNA亚克隆，可应用于西尼罗病毒全长cDNA克隆的制备。     

小鼠抗人小细胞肺癌单抗轻链可变区基因的体外扩增、克隆及序列分析

本文通过一对分别位于小鼠免疫球蛋白轻链可变区基因 FR1骨架区和 FR4骨架区的通用引物,利用 PCR 技术首次从小鼠抗人小细胞肺癌2F7杂交瘤细胞染色体组总 DNA 中直接扩增出相应的免疫球蛋白轻链可变区基因,扩增出的基因片段经引物上引进的两个限制性内切酶位点直接克隆到装有人免疫球蛋白轻链恒区的克隆载体 pGEM-7Zf( )-V_kPCR 中的 EcoR1和 BglⅡ内切酶位点之间.通过对其进行顺序分析,结果表明我们克隆得到了免疫球蛋白轻链可变区基因,其长度为318bp.     

HIV-1 nef基因的克隆及原核表达研究

目的:构建HIV-1 Nef基因的原核表达载体并在大肠杆菌中进行表达,初步优化其表达条件。方法:利用特异性引物PCR扩增获得HIV-1 Nef基因片段,PCR产物经限制性内切酶双酶切后连接载体pET24a(+),构建重组质粒pET24a(+)-Nef。经双酶切鉴定及序列测定后的重组质粒转化入E.coliBL21,IPTG诱导表达目的蛋白,优化表达条件,SDS-PAGE及Western blot分析鉴定表达产物。结果:PCR扩增获得618bpDNA片段,酶切鉴定结果表明HIV Nef基因已克隆入原核表达载体pET24a(+)中,测序证明序列正确。SDS-PAGE和Western blot分析证实重组菌诱导后可表达相对分子质量(Mr)符合预期的融合蛋白。0.1mmol/LIPTG在37℃诱导6h为最佳表达条件,重组蛋白表达量可由15.8%增加到43.9%。结论:在大肠杆菌中成功地表达了HIV Nef蛋白,并初步获得了最优化的表达条件。     

恶性疟原虫FCC—1／HN株环子孢子蛋白基因分枝杆菌——大肠杆穿梭表达重组质粒的构建及序列测定

本文对恶性疟原虫环子孢子蛋白(circumsporozoiteprotein,CSP)基因片段进行克隆和序列测定。根据恶性疟原虫837株基因编码序列设计合成一对引物,采用PCR技术从恶性疟原虫FCC-1/HN株基因组DNA中特异扩增CSP基因片段的Ⅰ区、中央重复区、重复区后可变区和Ⅱ区;经纯化的扩增产物用BamHⅠ和KpnⅠ双酶切后,定向克隆入大肠杆菌——分枝杆菌穿梭表达质粒,转化感受态大肠杆菌DH5α,重组克隆经抗性筛选和快速凝胶电泳鉴定,再经PCR和酶切鉴定,并对重组子进行序列测定。结果表明从恶性疟原虫FCC-1／HN株基因组DNA中可特异扩增出约1171bp的基因片段,阳性重组质粒经双酶切和PCR鉴定与预期的结果一致,序列测定表明所克隆的基因和编码环子孢子抗原的基因片段相符。     

异基因骨髓移植中PCR-SSP和RFLP对HLA-DRB、DPB1分型的应用

目的:探讨序列特异性引物聚合酶链反应（PCR-SSP）和聚合酶链反应限制性片段长度多态性分析（PCR-RFLP）对HLA-DRB、DPB1分型在异基因骨髓移植中应用的可行性。方法:应用19对不同的DRB抗原所对应等位基因序列特异性的引物,PCR扩增供受者各20个样本DRB,产物直接琼脂糖凝胶电泳分析;同时用另一对引物PCR扩增DPB1第二外显子,产物10种限制性内切酶酶切分析。结果:各DRB带清晰可辨,直接确定为该型;DPB1的多态性片段编码转换后确定其基因型;4例找到供者。结论:它们是异基因骨髓植前快速、精确和可靠的基因分型手段。     

弓形虫RH株微线体蛋白MIC3基因的克隆与表达

目的 克隆和表达弓形虫微线体蛋白MIC3基因。方法 从弓形虫RH株分离总的RNA,反转成cDNA.根据MIC3基因序列,设计合成一对引物,用聚合酶链式反应（PCR）方法从弓形虫cDNA中扩增MIC3基因片段,插入pGEM-T载体,并转化大肠杆菌Top10,经PCR、双酶切、测序验证后,将MIC3基因片段定向亚克隆到载体pET-28a中构建原核表达重组质粒pET-28a-MIC3,重组子在E.coli BL21中经IPTG诱导表达,并对表达产物进行SDS-PAGE和Western-blot分析。结果 从弓形虫RH株cDNA中扩增出792bp大小的MIC3基因片段并诱导表达27 300 Mr的重组MIC3蛋白。结论 成功构建和表达了弓形虫pET-28a-MIC3重组质粒,为弓形虫病诊断抗原和疫苗的研究奠定了基础。     

hGR小基因真核表达载体的构建及其在HeLa细胞中的表达

目的：构建用于体内剪接分析的人糖皮质激素受体（hGR）小基因真核表达载体。方法:以人基因组DNA为模板,设计特定的引物进行PCR扩增获得3.892 kb长的hGR小基因片段,并将其连入pMD18-TSimple载体中,限制性内切酶酶切鉴定后,再亚克隆到PcDNA3载体中,获得hGR小基因真核表达质粒PcDNA3-hGR并测序验证。Lipofectamine法转染PcDNA3-hGR至HeLa细胞,RT-PCR检测hGR小基因剪接异构体hGRα and hGRβ mRNA的表达。结果:限制性内切酶酶切和DNA测序分析证实克隆片段序列与GenBank目标序列一致；PcDNA3-hGR在HeLa细胞内成功表达剪接异构体hGRα和hGRβ。结论:hGR小基因真核表达载体构建成功，为进一步研究糖皮质激素受体基因外显子9的选择性剪接提供了细胞分子模型。     

iNOS基因和iNOS-VP1融合基因真核表达载体的构建及初步表达

目的 构建pcDNA3．1介导的诱导性一氧化氮合成酶（iNOS）的基因表达载体和pcDNA3．1介导的iNOS与柯萨奇病毒B组3型（CVB3）结构蛋白VP1融和基因的表达载体。方法 应用PCR扩增和DNA重组技术构建pcDNA3．1-iNOS和pcDNA3．1-iNOS—VP1表达载体；应用真核细胞转染技术及间接免疫荧光技术进行所构建的真核表达载体的初步表达和鉴定。结果 经PCR扩增技术用特异引物从质粒pKSiNOS分离编码iNOS开放阅读框架的cDNA，TA克隆于pMD19-T载体，根据设计引物时加入的酶切位点将插入片断亚克隆于表达载体pcDNA3．1；经PCR扩增技术用特异引物从质粒pCR2．1-VP1分离编码CVB3VP1结构蛋白的cDNA，TA克隆于pMD19-T载体，根据设计引物时加入的酶切位点将VP1亚克隆于iNOS的表达载体pcDNA3．1-iNOS，从而构建含有iNOS和VP1融合基因的真核表达载体。限制性内切酶分析、PCR鉴定和测序证实重组体peDNA3．1-iNOS和peDNA3．1-iN—OS—VP1插入片断的大小和方向正确且开放阅读框架的读码框不变；重组质粒peDNA3．1-iNOS和peDNA3．1-iNOS．VP1在HeLa细胞中均有表达，但表达效率较低。结论 获得含iNOS基因和iNOS—VP1融合基因的真核表达载体，并将重组质粒进行了初步表达，为体外iNOS抗CVB3作用的研究奠定了物质基础。     

恶性疟原虫红内期PF332抗原基因未知片段的体外扩增与克隆

根据恶性疟原虫FCCI／NH株PF332基因片段5’端巳知序列，设计台成了一条特异引物(SP)；报据PF332基因的结构特点，又设计合成了一条非特异引物(NSP)。应用低严谨PCR技术(LSPCR)，从恶性疟原虫FCC1／FN株基因组DNA中扩增出一系列PF332基因未知片段。利用T-A克隆法将一560bp大小的片段克隆入测序用PMD-18T载体。限制性内切酶酶切及PCR扩增鉴定表明重组正确。     

A modified restriction display PCR method in sample-labelling of DNA microarray

The restriction display PCR is a useful technique for studying the diversity of gene expression. This method involves ligating the digested genes with adapters and amplifying the gene fragments by PCR using universal and selective primers. In this study, we improved this restriction display PCR method by using Cy3-UP, a fluorescently labelled universal primer, in place of Cy3-dCTP in sample-labelling for DNA microarray. The results show that this new method increases significantly the sensitivity of the assay, and will have a wide application in the DNA microarray field.     

Differentiation of pathogenic Bartonella species by infrequent restriction site PCR

Infrequent restriction site PCR (IRS-PCR) is a recently described DNA fingerprinting technique based on selective amplification of restriction endonuclease-cleaved fragments. Bartonella isolates associated with human disease and related nonhuman isolates were analyzed by IRS-PCR genomic fingerprinting. Preparation of DNA templates began with double digestion using three different restriction endonuclease combinations. Combinations included the frequently cutting endonuclease HhaI in conjunction with an infrequently cutting endonuclease, EagI, SmaI, or XbaI. Digestion was followed by ligation of oligonucleotide adapters designed with ends complementary to the restriction endonuclease sites. Amplification of fragments flanked with an EagI, SmaI, or XbaI site in combination with an HhaI site produced a series of different-sized amplicons resolvable into patterns by polyacrylamide gel electrophoresis (PAGE). The pattern complexity was varied by the addition of selective nucleotides to the 3' ends of the EagI-, SmaI-, or XbaI-specific primers. Amplicons were also generated with fluorescently labeled primers and were subsequently resolved and detected by capillary electrophoresis. Analysis by traditional slab PAGE and capillary electrophoresis provided suitable resolution of patterns produced with the enzyme combinations EagI-HhaI and SmaI-HhaI. However, the combination of XbaI-HhaI produced too many fragments for sufficient resolution by traditional PAGE, thus requiring the better resolving properties of capillary electrophoresis. Due to the flexibility in modulating the pattern complexity and electrophoresis methods, these techniques allow for a high level of experimental optimization. The results provide evidence of the discriminatory power, ease of use, and flexibility of the IRS-PCR method as it applies to the identification of human-pathogenic Bartonella species.     

Evaluation of fluorescence-based amplified fragment length polymorphism analysis for molecular typing in hospital epidemiology: comparison with pulsed-field gel electrophoresis for typing strains of vancomycin-resistant Enterococcus faecium

Fluorescence-based amplified fragment length polymorphism (fbAFLP) is a novel assay based on the fluorescent analysis of an amplified subset of restriction fragments. The fbAFLP assay involves the selective PCR amplification of restriction fragments from a total digest of genomic DNA. The ligation of adapters with primer-specific sites coupled with primers containing selective nucleotides allowed the full potential of PCR to be realized while maintaining the advantages of restriction endonuclease analysis. Fluorescence-based fragment analysis with polyacrylamide gel electrophoresis provides the accurate band sizing required for homology assessment. The large number of phylogenetically informative characters obtained by fbAFLP is well suited for cluster analysis and database development. The method demonstrated excellent reproducibility and ease of performance and interpretation. We typed 30 epidemiologically well-characterized isolates of vancomycin-resistant enterococci from an outbreak in a university hospital by fbAFLP. Clustering of fbAFLP data matched epidemiological, microbiological, and pulsed-field gel electrophoresis data. This study demonstrates the unprecedented utility of fbAFLP for epidemiological investigation. Future developments in standardization and automation will set fbAFLP as the "gold standard" for molecular typing in epidemiology.     

Use of amplified fragment length polymorphism in molecular typing of Legionella pneumophila and application to epidemiological studies.

A novel method for molecular typing of organisms, amplified fragment length polymorphism analysis, was tested for its suitability in epidemiological studies in medical microbiology. Amplified fragment length polymorphism analysis, originally developed for typing crop plants, consists of a simple restriction-ligation reaction and a subsequent PCR amplification. In a single-step reaction, the genomic DNA is digested and the restriction fragments are ligated to specially constructed adapters. PCR amplification of such tagged restriction fragments with primers complementary to the adapters allows the detection of restriction fragment length polymorphisms upon resolution on agarose gels. The method is fast, efficient, and reproducible for typing strains of Legionella pneumophila isolated from both humans and the environment. The accuracy of the method was tested by comparison with standard restriction fragment length polymorphism typing performed with both a ribosomal and a genomic probe.     

Selective cloning of B cell hybridoma-specific rearranged immunoglobulin gene loci using the polymerase chain reaction

The use of conventional DNA cloning procedures to obtain productively rearranged Ig genes from B cell hybridomas for structure/function analysis of immunoglobulins is tedious and time-consuming. Here we describe a procedure based on PCR which permits rapid, selective isolation of DNA segments containing individual hybridoma-specific Ig gene rearrangements. The method, an adaptation of the so-called 'inverted PCR' technique (IPCR), can be applied most efficiently to specific genes where a preliminary restriction map is available from Southern blot analysis of the hybridoma genomic DNA. To achieve amplification of a given rearranged Ig locus, small amounts of total hybridoma DNA are digested to completion with a chosen restriction endonuclease and the fragments circularised by DNA ligase. Cleavage of the DNA circles using a second restriction enzyme, chosen specifically to cut 3' to a rearranged V-(D)-J exon, leads to linear DNA segments where the rearranged gene is now flanked by segments of known nucleotide sequence derived originally from the 3' region of the Ig H or L chain gene locus. This permits the selection of oligonucleotides that provide convergent primers for specific amplification of DNA segments containing the required gene rearrangement. Amplified DNA fragments can be cloned and rapidly characterised by sequence analysis.     

K562细胞株表达基因探针制作的探讨

目的　研究基因芯片探针的制备方法 ,为K5 6 2细胞基因表达谱芯片的制作及其在基因表达研究中应用打下基础。　方法　以人红白血病K5 6 2细胞株为材料 ,应用一种分离显示基因的新方法即限制性显示 (RD PCR)技术 ,分离DNA片段 ,作为基因芯片探针。　结果　分离到近千个大小在 2 0 0～ 5 0 0bp的基因片段 ,认为该方法可以克服DD PCR中出现的假阳性较多的缺点 ,简单易操作 ,且利用该方法分离的基因探针 ,制备DNA微集芯片 ,同全长cDNA探针制作芯片相比 ,其探针长度小且相对均一 ,杂交动力学易于控制。　结论　限制性显示技术为基因芯片探针的制备提供了一个全新的思路 ,并将大大加速基因芯片技术及其应用研究     

LuxS基因缺失的变形链球菌突变株的构建及鉴定

目的 通过同源重组法构建LuxS基因缺失的变形链球菌(Streptococcus mutans)突变株.方法 运用基因同源重组方法将红霉素抗性基因(Eymr)连接到PCR扩增LuxS基因两端区域产生的2个基因片段之间,并共同插入到pUCl9载体的多克隆位点中,构建出带红霉素抗性标志的缺失突变载体pUCluxKO.将突变载体转化到含完整LuxS基因的突变受体变形链球菌标准株中,红霉素筛选出LuxS基因缺失的变形链球菌突变株,并经PCR、生物荧光检测及DNA测序鉴定.结果 构建的突变载体经限制性内切核酸酶酶切分析显示,产生的条带与设计结果完全一致.PCR方法扩增突变株LuxS和Eymr基因显示,LuxS基因已被完整敲除掉,经生物荧光检测,突变株不能诱导哈氏弧菌(Vibrio harveyi)BBl70的生物发光,说明不能产生信号分子AI-2(autoinducer-2).DNA测序证实筛选得到了LuxS基因缺失的变形链球菌突变株.连续传代培养后证实,变形链球菌LuxS基因突变株具有良好的稳定性.结论 成功构建出LuxS基因缺失的变形链球菌突变株,为研究LuxS基因对变形链球菌致龋毒力的影响奠定了基础.     

Two-step polymerase chain reactions and restriction endonuclease analyses detect and differentiate ompA DNA of Chlamydia spp.

Specific and sensitive amplification of major outer membrane protein (MOMP) gene (ompA) DNA sequences of Chlamydia species with various MOMP genotypes was achieved by a two-step polymerase chain reaction (PCR). Degenerate, inosine-containing oligonucleotide primers homologous to the 5' and 3' ends of the translated regions of all chlamydial MOMP genes were used in a PCR to amplify a DNA fragment of approximately 1,120 bp. A portion of this DNA fragment was amplified in a second genus-specific reaction that yielded a DNA fragment of approximately 930 bp. A pair of degenerate oligonucleotide primers homologous to internal sequences of the primary DNA fragment was used in this PCR. This method detected three cognate chlamydial genomes in a background of 1 microgram of unrelated DNA. MOMP genes of 13 representative chlamydial MOMP genotypes of the species C. trachomatis, C. pneumoniae, and C. psittaci were amplified. In a secondary PCR, group-specific detection was achieved by the simultaneous use of one genus-specific primer and three primers derived from different fingerprint regions of three major groups of chlamydiae. This multiplex PCR differentiated the groups by the length of the amplified DNA fragments and detected the simultaneous presence of DNA sequences of the Chlamydia spp. with different MOMP genotypes. Further differentiation as ompA restriction fragment length polymorphism types among all chlamydial strains with the various MOMP genotypes analyzed here was achieved by restriction endonuclease analysis of the secondary PCR products. DNA sequences corresponding to the ompA restriction fragment length polymorphism type B577 of C. psittaci were detected in two of seven milk samples from cases of bovine mastitis.     

AFLP allows the identification of genomic markers of ruminant Chlamydia psittaci strains useful for typing and epidemiological studies

Amplified fragment length polymorphism (AFLP), a novel method for molecular typing, was evaluated for its ability to differentiate among a group of highly related Chiamydia psittaci strains isolated from ruminants and belonging to serotype 1. A total set of 12 strains were included in this study, 10 strains inducing abortion in ruminants and 2 strains from faecal samples. For the AFLP analysis, the total purified genomic DNA of each strain was submitted to a one-step digestion-ligation reaction for 3 h at 37°C. DNA was digested with a single restriction endonuclease Mspl and ligated to specially constructed adapters. Subsequently, restricted fragments were selectively amplified under high stringency PCR conditions using primers complementary to the adapters. Amplified products were then resolved on agarose gel electrophoresis. The method is easy to perform, fast and reproducible. AFLP enabled characterization of C. psittaci strains at the infra-subspecific level. Thus, AFLP led to the identification of a cluster of strains on the basis of their AFLP patterns, constituted by French chlamydial isolates. It also permitted differentiation among strains in relation to host origin and to clinical syndromes. These data confirmed the highly discriminative power of AFLP towards the differentiation of closely related ruminant C. psittaci strains. The analysis will need to be applied to more samples to check the usefulness of AFLP markers in epidemiological and evolutionary studies.